1. Field of the Invention
This invention pertains to treatments of disorders associated, at least in part, with neural activity. These may include, without limitation, gastrointestinal, pancreo-biliary, cardio-respiratory and central nervous system disorders (including neurological and psychiatric, psychological and panic disorders). More particularly, this invention pertains to treatment of such disorders through management of neural impulse stimulation and blocking
2. Description of the Prior Art
A. Functional Gastrointestinal Disorders (FGIDs)
Functional Gastrointestinal Disorders (FGIDs) are a diagnostic grouping having diagnostic criteria based on symptomatology, because the pathophysiology of these diseases is multifactorial with some pathophysiologic mechanisms in common. FGIDs are thought to be due to altered autonomic nervous system balance and to be pathophysiological combinations of: (1) abnormal GI motility; (2) visceral hypersensitivity; and, (3) brain-gut interactions. Tougas, “The Autonomic Nervous System in Functional Bowel Disorders”, Gut, Vol. 47 (Suppl IV), pp. iv78-iv80 (2000) and Drossman, “Rome II: A Multinational Consensus Document on Gastrointestinal Disorders—The Functional Gastrointestinal Disorders and the Rome II Process”, Gut, Vol. 45 (Suppl II):II1-II5 (1999). The FGIDs of interest to the present invention are functional dyspepsia (dysmotility-like) and irritable bowel syndrome (IBS).
1. Functional Dyspepsia (Dysmotility-Like)
Functional dyspepsia (dysmotility-like), is diagnosed when a patient's symptoms, in the absence of other organic disease likely to explain the symptoms, include persistent or recurrent pain or discomfort centered in the upper abdomen that may be accompanied by upper abdominal fullness, early satiety, bloating or nausea. Talley et al., “Rome II: A Multinational Consensus Document on Gastrointestinal Disorders—Functional Gastroduodenal Disorders” Gut, Vol. 45 (Suppl II), pp. I37-II42 (1999).
A spectrum of dysmotilities has been documented in patients with functional dyspepsia. These include delayed gastric emptying of solids and liquids, reduced vagal tone, gastric dysrhythmias and impaired gastric accommodation. Furthermore, some studies have found good correlation between symptoms and indices of dysmotility, while others have not. Stanghellini V, et al., “Delayed Gastric Emptying of Solids in Patients with Functional Dyspepsia”, Gastroenterol, (1996) 110:1036-1042. Undeland K A, et al., “Wide Gastric Antrum and Low Vagal Tone in Patients with Diabetes Mellitus Type 1 Compared to Patients with Functional Dyspepsia and Healthy Individuals”, Dig Dis Sci, (1996) 41:9-16. Tack J, et al., “Role of Impaired Gastric Accommodation to a Meal in Functional Dyspepsia”, Gastroenterol, (1998) 115:1346-1352. Wilmer A, et al., “Ambulatory Gastrojejunal Manometry in Severe Motility-like Dyspepsia: Lack of Correlation between Dysmotility, Symptoms and Gastric Emptying”, Gut, (1998) 42:235-242. Tack J, et al., “Symptom Pattern and Gastric Emptying Rate Assessed by the Octanoic Acid Breath Test in Functional Dyspepsia” [abstract]. Gastroenterol, (1998) 114:A301. Cuomo R, et al., “Functional Dyspepsia Symptoms, Gastric Emptying and Satiety Provocation Test: Analysis of Relationships”, Scand J Gastroenterol, (2001) 36:1030-1036. Sarnelli G, et al., “Symptoms Associated with Impaired Gastric Emptying of Solids and Liquids in Functional Dyspepsia”, Am J Gastroenterol, (2003) 98:783-788.
2. Irritable Bowel Syndrome (IBS)
The second FGID of interest, IBS, is diagnosed when a patient's symptoms include persistent abdominal pain or discomfort, in the absence of other explanatory organic disease, along with at least two of the following: relief of pain with defecation, onset of symptoms associated with a change in frequency of stools and/or onset of symptoms associated with a change in appearance/form of stools. Thompson W G, et al., “Rome II: A Multinational Consensus Document on Gastrointestinal Disorders—Functional Bowel Disorders and Functional Abdominal Pain”, Gut, (1999);45(Suppl II):II43-II47.
In addition to colonic dysmotility, a number of other GI motility abnormalities have been identified, including delayed gastric emptying, gastroparesis, and small intestine motility abnormalities. Vassallo M J, et al., “Colonic Tone and Motility in Patients with Irritable Bowel Syndrome”, Mayo Clin Proc, (1992);67:725-731. Van Wijk H J, et al., “Gastric Emptying and Dyspeptic Symptoms in the Irritable Bowel Syndrome”, Scand J Gastroenterol, (1992);27:99-102. Evans P R, et al., “Gastroparesis and Small Bowel Dysmotility in Irritable Bowel Syndrome”, Dig Dis Sci (1997);42:2087-2093. Cann P A, et al. “Irritable Bowel Syndrome: Relationship of Disorders in the Transit of a Single Solid Meal to Symptoms Patterns”, Gut, (1983);24:405-411. Kellow J E, et al., “Dysmotility of the Small Intestine in Irritable Bowel Syndrome“, Gut, (1988);29:1236-1243. Evans P R, et al., ”Jejunal Sensorimotor Dysfunction in Irritable Bowel Syndrome: Clinical and Psychosocial Features“, Gastroenterol, (1996);110:393-404. Schmidt T, et al., ”Ambulatory 24-Hour Jejunal Motility in Diarrhea-Predominant Irritable Bowel Syndrome“, J Gastroenterol, (1996);31:581-589. Simren M, et al., ”Abnormal Propagation Pattern of Duodenal Pressure Waves in the Irritable Bowel Syndrome (IBS)”, Dig Dis Sci, (2000);45:2151-2161.
A related finding is that patients with constipation-predominant IBS have evidence of decreased vagal tone, while diarrhea-predominant IBS is associated with evidence of increased sympathetic activity. Aggarwal A, et al., “Predominant Symptoms in Irritable Bowel Syndrome Correlate with Specific Autonomic Nervous system Abnormalities”, Gastroenterol, (1994);106:945-950.
There is no cure for IBS. Treatments include supportive palliative care (antidiarrheals, dietary modification and counseling).
A recently approved drug to treat selected patients with FGIDs is tegaserod maleate sold under the tradename “Zelnorm®” by Novartis Pharmaceuticals Corp., East Hanover, N.J., USA. The product literature on Zelnorm recognizes the enteric nervous system is a key element in treating IBS. The literature suggests Zelnorm® acts to enhance basal motor activity and to normalize impaired motility. Novartis product description, Zelnorm®, July 2002 (T2002-19). Zelnorm's approved use is limited to females with constipation-related IBS. It is for short-term use only.
B. Gastroparesis
The third disease indication discussed here, gastroparesis (or delayed gastric emptying) is associated with upper GI symptoms such as nausea, vomiting fullness, bloating and early satiety. Gastroparesis can be caused by many underlying conditions. The most important, because of chronicity and prevalence, are diabetes, idiopathic and post-surgical. Hornbuckle K, et al. “The Diagnosis and Work-Up of the Patient with Gastroparesis”, J Clin Gastroenterol, (2000);30:117-124. GI dysmotility in the form of delayed gastric emptying is, by definition, present in these patients.
In patients with Type 1 diabetes mellitus and delayed gastric emptying, there appears to be a relationship between delayed gastric emptying and low vagal tone. Merio R, et al., “Slow Gastric Emptying in Type 1 Diabetes: Relation to Autonomic and Peripheral Neuropathy, Blood Glucose, and Glycemic Control”, Diabetes Care, (1997);20:419-423. A related finding is that patients with Type 1 diabetes have low vagal tone in association with increased gastric antral size, possibly contributing to the dysmotility-associated symptoms seen in these patients. Undeland K A, et al., “Wide Gastric Antrum and Low Vagal Tone in Patients with Diabetes Mellitus Type 1 Compared to Patients with Functional Dyspepsia and Healthy Individuals”, Dig Dis Sci, (1996);41:9-16.
The current treatments for gastroparesis are far from satisfactory. They include supportive care, such as dietary modification, prokinetic drugs, and; when required, interventions such as intravenous fluids and placement of a nasogastric tube may be needed.
C. Gastroesophageal Reflux Disease (GERD)
The fourth indication, GERD, can be associated with a wide spectrum of symptoms, including dyspepsia, reflux of gastric contents into the mouth, dysphagia, persistent cough, refractory hyperreactive airway disease and even chronic serous otitis media. Sontag S J, et al., “Asthmatics with Gastroesophageal Reflux: Long Term Results of a Randomized Trial of Medical and Surgical Antireflux Therapies”, Am J Gastroenterol, (2003);98:987-999. Poelmans J, et al., “Prospective Study on the Incidence of Chronic Ear Complaints Related to Gastroesophageal Reflux and on the Outcome of Antireflux Therapy”, Ann Otol Rhinol Laryngol, (2002);111:933-938.
GERD is considered to be a chronic condition for which long-term medical therapy and/or surgical therapy is often deemed necessary, in significant part because esophageal adenocarcinoma is sometimes a consequence of GERD. DeVault K R, et al., “Updated Guidelines for the Diagnosis and Treatment of Gastroesophageal Reflux Disease”, Am J Gastroenterol, (1999);94:1434-1442. Lagergren J, et al., “Symptomatic Gastroesophageal Reflux as a Risk Factor for Esophageal Adenocarcinoma”, New Engl J Med, (1999);340:825-831.
The underlying pathophysiological mechanisms in GERD are considered to be transient lower esophageal relaxations (TLESRs) in the presence of either an inadequate pressure gradient between the stomach and the esophagus across the lower esophageal sphincter and/or low amplitude esophageal activity at times when gastric contents do reflux into the esophagus. In addition, gastric distention is thought to be associated with an increase in TLESRs. Mittal R K, et al., “Mechanism of Disease: The Esophagogastric Junction”, New Engl J Med, (1997);336:924-932. Scheffer R C, et al., “Elicitation of Transient Lower Oesophageal Sphincter Relaxations in Response to Gastric Distension”, Neurogastroenterol Motil, (2002);14:647-655.
GERD is generally considered to be the result of a motility disorder which permits the abnormal and prolonged exposure of the esophageal lumen to acidic gastric contents. Hunt, “The Relationship Between The Control Of pH And Healing And Symptom Relief In Gastro-Oesophageal Reflux Disease”, Ailment Pharmacol Ther., 9 (Suppl. 1) pp. 3-7 (1995). Many factors are believed to contribute to the onset of GERD. These include transient lower esophageal sphincter relaxations (as previously described), decreased LES resting tone, delayed stomach emptying and an ineffective esophageal clearance.
Certain drugs have had some effectiveness at controlling GERD but fail to treat underlying causes of the disease. Examples of such drugs are H2-receptor antagonists (which control gastric acid secretion in the basal state) and proton pump inhibitors (which control meal-stimulated acid secretion). Hunt, id. Both classes of drugs can raise intragastric pH to or about 4 for varying durations. Hunt, supra.
Surgery treatments are also employed for the treatment of GERD and include techniques for bulking the lower esophageal sphincter such as fundoplication and techniques described in U.S. Pat. No. 6,098,629 Johnson et al, Aug. 8, 2000. Other surgical techniques include placement of pacemakers for stimulating muscle contractions in the esophageal sphincter, the stomach muscles or in the pyloric valve. U.S. Pat. No. 6,104,955 to Bourgeois, U.S. Pat. No. 5,861,014 to Familoni.
A summary of GERD treatments can be found in DeVault, et al., “Updated Guidelines for the Diagnosis and Treatment of Gastroesophageal Reflux Disease”, Amer. J. of Gastroenterology, Vol. 94, No. 6, pp. 1434-1442 (1999).
Notwithstanding multiple attempts at various types of treatment, GERD continues to be a serious disease proving to be difficult to treat by any of the foregoing prior art techniques. In view of the foregoing and notwithstanding various efforts exemplified in the prior art, there remains a need for an effective treatment for GERD. It is an object of the present invention to provide a novel treatment and novel apparatus for the treatment of GERD.
D. Electrical Stimulation to Treat GI Disorders
Treatment of gastrointestinal diseases through nerve stimulation have been suggested. For example, U.S. Pat. No. 6,238,423 to Bardy dated May 29, 2001 describes a constipation treatment involving electrical stimulation of the muscles or related nerves of the gut. U.S. Pat. No. 6,571,127 to Ben-Haim et al. dated May 27, 2003 describes increasing motility by applying an electrical field to the GI tract. U.S. Pat. No. 5,540,730 to Terry, Jr. et al., dated Jul. 30, 1996 describes a motility treatment involving vagal stimulation to alter GI contractions in response to a sense condition indicative of need for treatment. The '730 patent also uses a definition of dysmotility more restrictive than in the present application. In the '730 patent, dysmotility is described as hyper- or hypo-contractility. In the present application, dysmotility is a broader concept to refer to all abnormalities of gastric emptying or bowel transfer regardless of cause. U.S. Pat. No. 6,610,713 to Tracey dated Aug. 26, 2003 describes inhibiting release of a proinflammatory cytokine by treating a cell with a cholinergic agonist by stimulating efferent vagus nerve activity to inhibit the inflammatory cytokine cascade.
A substantial body of literature is developed on nerve stimulation. For example, in Dapoigny et al., “Vagal influence on colonic motor activity in conscious nonhuman primates”, Am. J. Physiol., 262: G231-G236 (1992), vagal influence on colonic motor activity was investigated in conscious monkeys. To block antidromic interference, the vagus was blocked via vagal cooling and a vagal stimulation electrode was implanted distal to the vagal block. It was noted that vagal efferent stimulation increased contractile frequency and that the vagus has either a direct or indirect influence on fasting and fed colonic motor activity throughout the colon, and that a non-adrenergic, noncholinergic inhibitory pathway is under vagal control.
Colonic and gastric stimulation are also described in a number of articles associated with M. P. Mintchev. These include: Mintchev, et al., “Electrogastrographic impact of multi-site functional gastric electrical stimulation”, J. of Medical Eng. & Tech., Vol. 23, No. 1 pp. 5-9 (1999); Rashev, et al., “Three-dimensional static parametric modeling of phasic colonic contractions for the purpose of microprocessor-controlled functional stimulation”, J. of Medical Eng. & Tech., Vol. 25, No. 3 pp. 85-96 (2001); Lin et al., “Hardware—software co-design of portable functional gastrointestinal stimulator system”, J. of Medical Eng. & Tech., Vol. 27, No. 4 pp. 164-177 (2003); Amaris et al., “Microprocessor controlled movement of solid colonic content using sequential neural electrical stimulation”, Gut, 50: pp 475-479 (2002) and Rashev et al., “Microprocessor-Controlled Colonic Peristalsis”, Digestive Diseases and Sciences, Vol. 47, No. 5, pp. 1034-1048 (2002).
The foregoing references describe nerve stimulation to stimulate muscular contraction in the GI tract. As will be more fully discussed, the present invention utilizes vagal stimulation to improve vagal tone (similar in concept to improving cardiac electrical tone through cardiac pacing) and/or to treat GI disorders by altering the nature of duodenum contents by stimulation pancreatic and biliary output. The invention is also applicable to treating other diseases such as neuropsychiatric disorders.
Vagal tone has been shown to be associated with dyspepsia. Hjelland, et al., “Vagal tone and meal-induced abdominal symptoms in healthy subjects”, Digestion, 65: 172-176 (2002). Also, Hausken, et al., “Low Vagal Tone and Antral Dysmotility in Patients with Functional Dyspepsia”, Psychosomatic Medicine, 55: 12-22 (1993). Also, decreased vagal tone has been associated with irritable bowel syndrome. Heitkemper, et al., “Evidence for Automatic Nervous System Imbalance in Women with Irritable Bowel Syndrome”, Digestive Diseases and Sciences, Vol. 43, No. 9, pp. 2093-2098 (1998).
Also, as will be discussed, the present invention includes, in several embodiments, a blocking of a nerve (such as the vagal nerve) to avoid antidromic influences during stimulation. Cryogenic nerve blocking of the vagus is described in Dapoigny et al., “Vagal influence on colonic motor activity in conscious nonhuman primates”, Am. J. Physiol., 262: G231-G236 (1992). Electrically induced nerve blocking is described in Van Den Honert, et al., “Generation of Unidirectionally Propagated Action Potentials in a Peripheral Nerve by Brief Stimuli”, Science, Vol. 206, pp. 1311-1312. An electrical nerve block is described in Solomonow, et al., “Control of Muscle Contractile Force through Indirect High-Frequency Stimulation”, Am. J. of Physical Medicine, Vol. 62, No. 2, pp. 71-82 (1983) and Petrofsky, et al., “Impact of Recruitment Order on Electrode Design for Neural Prosthetics of Skeletal Muscle”, Am. J. of Physical Medicine, Vol. 60, No.5, pp. 243-253 (1981). A neural prosthesis with an electrical nerve block is also described in U.S. Patent Application Publication No. US 2002/0055779 A1 to Andrews published May 9, 2002. A cryogenic vagal block and resulting effect on gastric emptying are described in Paterson C A, et al., “Determinants of Occurrence and Volume of Transpyloric Flow During Gastric Emptying of Liquids in Dogs: Importance of Vagal Input”, Dig Dis Sci, (2000);45:1509-1516.